Mobile weed burner system



March 27, 1951 O. L. GARRETSON ETAL MOBILE WEED BURNER SYSTEM Filed Dec.

JNVENTORS A.W.PECK O. L. GARRETSON YAI Patented Mar. 27, 1951 UNITED STATES .TENT QFFICE MOBILE WEED BURNER SYSTEM Application December 29, 1945, Serial No. 638,407

1 Claim.

This invention relates to Vaporizers. In one of its more specific aspects it relates to Vaporizers for use with liquefied petroleum gases. In a still more specific aspect it relates to Vaporizers which are adapted for use in conjunction with tractorweed burner combinations.

Flame methods for the destruction of weeds have gained in usage in the cultivation of certain crops as a substitute for mechanical cultivation or cutting methods and especially for hand labor methods. It is for the purpose of further extending the use of flame methods for weed killing and/or cultivation in view of economical considerations and savings in labor that our invention is disclosed.

Liquefied petroleum gases are now used as fuel in such weed burning operations and as fuel for internal combustion engines. The use of this type of material as engine fuel presents few problems other than those occasioned by a need for retaining the liquefied fuel under pressure. The rate of evaporation is not sufficiently great as to cause difficulty for engine fuel purposes, but when one source of liquefied fuel is used for the Weed burning burners and for a tractor engine, the latent heat of vaporization of the liquid often so chills the liquid that the rate of evaporation is retarded to such an extent that the weed burners do not properly function. It is for the purpose of overcoming this difficulty that our invention is directed.

One object of our invention is to provide a liquid hydrocarbon fuel vaporizer for use with weed burning equipment on a tractor.

Another object of our invention is to provide a liquid hydrocarbon fuel vaporizer for use with weed burning equipment on tractors wherein the vaporizer serves to vaporize fuel for the tractor as well as for the burner.

Still another object of our invention is to provide a liquid hydrocarbon fuel vaporizer for use with weed burning equipment on tractors whereby vaporized fuel, during times of low fuel requirement, is transmitted to points of consumption at a temperature sufficiently low as not to be destructive to delicate equipment with which I tached drawing forms a part of this specification.

The drawing represents diagrammatically a preferred form of the apparatus of our invention in conjunction with a tractor-weed burner assembly.

Referring to the drawing, a tractor l consists of conventional tractor elements, as wheels 2, an engine 3, a carburetor 4, a body 5, an exhaust pipe 6, a liquid hydrocarbon fuel tank I, and other parts not specifically shown.

The tractor may be equipped with one or more burners 8 adapted especially to the burning of weeds. The fuel tank 1 is intended to furnish fuel for the weed burners 8 and to the carburetor 4 and engine 3 for the propulsion of the tractor. The evaporation of liquefied petroleum gas at rates sufficient for the operation of the weed burners and for the tractor engine has presented a serious problem on account of the refrigeration properties possessed by such normally gaseous hydrocarbons. To solve the evaporation problem we have devised an evaporator 9 which is intended to be operated in conjunction with the exhaust pipe 6 from the tractor engine. Such an evaporator is in reality, a simple mechanisrn, consisting essentially of an enclosed cyl inder having an opening in either end wall for insertion of the exhaust pipe. The enclosed cylinder thus is composed of a cylindrical wall l0 surrounding the exhaust pipe so as to provide an annular space l3 between the wall If! and the exhaust pipe. End plates II serve to close the ends of the cylinder I0 and each plate has an opening for insertion of the exhaust pipe 6. This combination is intended to serve as an evaporating heat exchanger since liquefied petroleum gas from the storage tank 1 flows under its own pressure through a flow line l2 into the annular space I3. This space'is maintained at a high temperature by the passage of engine exhaust gases through the exhaust pipe 6 and the heat is utilized in transforming the fuel from the liquid form to the gaseous form, in which form it is suitable for burner and carburetor use.

The exhaust pipes of tractors ordinarily become quite hot, consequently ample heat for this vaporization is usually available even under full burner load conditions. We have found that at times when the weed burners 8 are not in use and evaporation rates are low (for carburetor use only) that the temperature of the evaporated fuel may become excessively high and under certain conditions may destroy such regulator diaphragms and seats as come in contact with the high temperature gas. To prevent such possible destruction of vital parts, we have provided a cooler 16 for lowering the temperature of the hot gas.

Such a cooler 16 is for the most part a liquidto-gas heat exchanger and consists of the inner liquid carrying tube [2 and an outer tube ll. The space between these tubes may be termed an annular space and serves to carry the evaporated fuel or hydrocarbon gas from the evaporator 9 to a manifold 18. From the manifold 8 a tube !9 extends to the carburetor 3, and a tube 29 extends to the weed burners 8. Valves 2! and 22 are provided in tubes 89 and 29, respectively, for manual control of flow of gas therethrough. Thus in case it is desired to close off the burners while the tractor is traveling from field to field or from shed to field, etc., valve 22 may be closed.

At the manifold point i8 and at connection points23 and 29, substantially any type of connections desired may be used. These joints and connections, however, should be of such type and of such materials as to withstand the temperatures of the hot gases and to withstand vibration, stresses and strains characteristic of such equipment.

The fuel tank I should preferably be located at a point remote from the burners 8 to minimize dangers resulting from transfer of heat from the burners to the tank. When liquid propane is used as the liquefied petroleum gas fuel, the tank will need to withstand rather high pressure since propane has a Reid vapor pressure of about 180 pounds per square inch (at 100 F.)

A mufiler, not shown, may be used on the tractor exhaust if desired, for obvious reasons. If

used, however, the muffler should preferably be placed on the downstream side of the evaporator 8 with respect to the direction of flow of exhaust gases.

The relatively cool liquid passing through tube I2 in heat exchange with the hot gases in the annular space 25 has been found to impart sufficient cooling to the gas as to prevent destructron of any fragile and easily burned apparatus parts such as regulator diaphragms mentioned hereinbefore.

This exhaust pipe-vaporizer unit should be well constructed and especially so from the point of view of gas leakage. Exhaust gas should not leak into the vaporizer nor should petroleum gas be permitted to leak into the exhaust pipe.

Materials of construction may be selected from among those commercially available. They should be able to withstand the gas engine exhaust pipe temperature.

As mentioned hereinbefore liquefied propane I propane liquid should be constructed of sufficiently heavy material as to withstand propane pressures. In order to burn propane in the equip ment as hereindescribed, pressure regulators, pressure reducers, automatic valves and the like will need be installed and used at certain points. However, the use of such auxiliary equipment forms no part of our invention, since the use of same is well known to those skilled in the art. Thus, by preference pressure reducers may be located at such points that the propane or other liquefied petroleum gas may be vaporized at substantially atmospheric pressure, or may be vaporized at propane or other storage pressure, as desired.

It will be obvious to those skilled in the art that many modifications of our invention may be made and yet remain within the intended spirit and scope of our invention.

Having described our invention, we claim:

In a mobile weed burning system including an internal combustion engine power plant and a weed burner, a heat exchange system for vaporizing liquefied petroleum gas as fuel for said internal combustion engine and said weed burner, comprising in combination an exhaust pipe extending from said internal combustion engine; a jacket surrounding at least a portion of said exhaust pipe and closed thereon so as to form an enclosed vaporizer chamber therebetween; a liquefied petroleum gas storage tank; liquefied petroleum gas conduit means extending from the lower extremity of said storage tank to said vaporizer chamber; a manifold chamber surrounding said liquefied petroleum gas conduit means and spaced from said vaporizer chamber; a vapor conduit, surrounding said liquefied petroleum gas conduit means so as to form a gas passage there between, extending from said vaporizer to said manifold chamber; and outlet conduits extending from said manifold chamber for connection to said internal combustion engine and said weed burner.

OWEN L. GARRETSON. ALVIN W. PECK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 594,282 Rambaud Nov. 23, 1897 1,373,477 Angus Apr. 5, 1921 1,390,639 Porter Sept. 13, 1921 1,528,930 La Plant et a1 Mar. 10, 1925 1,835,887 Mackey Dec. 8, 1931 1,905,971 Davisson et al. Apr. 25, 1933 2,150,764 Farineau Mar. 14, 1939 2,188,072 Brown Jan. 23, 1940 2,309,813 Whiting Feb. 2, 1943 

